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How-To: 4.0L SOHC/OHV Underdrive Pulley Kit Install


Old 03-15-2011
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How-To: 4.0L SOHC/OHV Underdrive Pulley Kit Install

How-To : 4.0L SOHC/OHV Underdog Underdrive Pulley Kit Install

Tools Required: 7mm socket
8mm socket
10mm socket
13mm socket
15mm socket
19mm socket
24”+ Breaker bar or Impact wrench
” socket wrench
3/8” socket wrench
” socket wrench
Flathead screwdriver
Adjustable strap wrench
Harmonic Balancer Puller Tool (or something similar)(Rent at PepBoys/Autozone)
Fan Clutch removal tool (rent at PepBoys/Autozone)
Lots of Patience

Materials Needed: 4.0L 5 piece Underdrive Pulley Kit from Underdog Performance @ to include :

4.0 ASP Underdrive Crank Pulley
4.0 Underdrive Water Pump Pulley (red or blue)
4.0 Overdrive Alternator Pulley (red or blue)
4.0 Stock sized Idler Pulley (red or blue)
4.0 Stock sized Water Pump Pulley (red or blue)

Gatorback belt : Part # 4060865 (Ordered mine from Amazon)
Crankshaft bolt : Ford Part # E7RY6A340B

This How-To MIGHT help:

Time Required: 3-6 hours

Difficulty: Moderate-Difficult (5-8) LOL 

Step 1: Remove the intake cover – 3 bolts – 7mm
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Step 2: Unclip air box, loosen hose clamps on air intake hose (flathead) and remove intake hose and air box lid
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Fan Clutch removal tool : You will use the 57mm and 36mm wrenches
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Step 3: Put the 57mm fan clutch wrench around the 4 bolts that hold the water pump pulley on. Then put the 36mm wrench on the nut for the fan. Loosen the fan by pushing the 57mm to the right… 36mm to the left. It will take some muscle to break it free. Spin fan until it comes off of the water pump pulley.
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Step 4: Remove 2 bolts holding on the fan shroud (10mm)
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Step 5: Pull Up and remove Fan shroud and Fan
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Step 6: Using a 3/8” socket wrench, put it into square hole on belt tensioner and push down to loosen tension on belt; then remove the belt
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NOTICE: At this point, I had already installed the Stock sized Idler pulley and the stock-sized water pump pulley (3 bolts) on an earlier install attempt. I will include the steps, but there are no pictures.

Step 7: Using a 15mm socket, remove the stock idler pulley.

Step 8: Install aftermarket Stock-sized idler pulley.

NOTICE: You will need to re-use the bolt, but I had to remove the washer on the outside part of the pulley because it was getting caught on the lock-ring on the new pulley and wouldn’t allow it to spin.
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Step 9: Using a 10mm socket, remove the stock water pump pulley (3 bolts). You can use a flathead screwdriver… or a strap wrench to hold the pulley from moving while you loosen the 3 bolts holding the pulley on. Pull hard, the pulley will come off.

Step 10: Install aftermarket Stock-sized water pump pulley (3 bolts). It might be difficult to install, but just tighten the bolts like you would a tire… it will get on there eventually.

Step 11: Use the 57mm fan clutch wrench and a 10mm socket to remove the 4 bolts holding the stock water pump pulley (4 bolts) off.
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Step 12: Install new Underdrive Water pump pulley with 4 bolts. (Sorry, No picture)

NOTICE: This is where things can get difficult, especially if you do not have the right tools, and a good friend to help.

Step 13: Using a 19mm deep socket, and a large breaker bar, place the socket on the crankshaft bolt (inside the hole on the crankshaft pulley) and rest the breaker bar on top of the driver side of the frame. Go into the cab, and turn it over to “bump” the starter… DO NOT CRANK THE MOTOR. This should break the bolt free, and you can loosen it the rest of the way by hand.

NOTICE: You can break the bolt free by using a strap wrench and a LOT of muscle to break it free, the bolt is torqued on and very difficult to break free. OR.. you can try to fit an impact wrench on there if space permits (might need to remove the radiator).
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Step 14: Using a 8mm socket, remove Crankshaft Position Sensor (2 bolts). Then pinch the metal clip and pull sensor off of the wiring harness.

NOTICE: You want to remove this because it can be broken easily, and your engine will not start if it is not there… ask me how I know.

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Step 15: Remove pulley using a harmonic balancer removal tool. Different "stud" lengths will be helpful as the clearance is tight between it and the radiator.

NOTICE: You will use the bolts that come with the kit. Most puller tools don’t have long enough bolts, even the universal ones.

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Note the difference in size between the stock crank pulley and the underdrive pulley. Stock pulley on the left, underdog pulley on the right.

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Step 16: Remove plastic collar from original pulley and install it in underdog 4.0 pulley. I used the puller tool, but a flat tip screwdriver will suffice. Be careful not to break it. Install this piece on the new pulley.

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Step 17: Prep the new pulley per directions included with the kit. RTV Silicone and grease will be needed. I marked the key slot on the exterior of the pulley with a grease crayon. This made positioning the pulley onto the crank shaft easier. You can "bump" the starter to move the keyway into a more visible location.

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Step 18: Set the pulley onto the shaft so that the keyways are line up. Insert the enclosed longer pulley bolt (included in the kit) and screw it about half way down. Remove this bolt and install the original crank bolt until tight.

Step 19: Wrap your adjustable strap wrench around your new pulley to hold it tight from moving. Using your torque wrench, tighten the new crank bolt to specs (80 ft/lbs).

Step 20: Install your new belt by loosening tension on the tensioner.

NOTICE: You should have a drawing of how your belt should be ran on top of your header panel.

Step 21: Re-install fan and shroud.

Step 22: Re-install intake and cover.


End Result:

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Last edited by 98liftedranger; 11-28-2011 at 11:48 AM.
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Old 02-16-2013
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do they even sell these anymore i cant find any pulley kits anywhere
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Old 02-16-2013
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I think he went out of business. You can probably still get an underdrive pulley from ASP Racing. It looks like they have a 25% Underdrive pulley for $265... might contact them to see if it will work for your 4.0.

ASP Racing - Ford Performance Pulleys
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Old 02-16-2013
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Did you notice a difference after doing the kit ? Was it worth it
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Old 02-17-2013
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I did notice a bit of a difference. With my 33's it helped give a little pep back. I was due for a new pulley anyway because mine was rattling (something inside broke loose), and for the cost of a stock one ($250), I thought i was worth it to spend a few extra dollars to upgrade and try it out.

It's more of a seat-of-the-pants feel, and less of a noticeable gain as far as HP or MPG's. I never had it dynoed before or after to give any real numbers. I'm sure with a good tune, it might be more useful.
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